Abstract
The global usage of veterinary antibiotics is significant. Antibiotics can be released into aquatic environments and elicit toxic effects on non-target organisms. In this study, the growth characteristics and toxin release of the cyanobacterium Microcystis aeruginosa (M. aeruginosa) were examined to investigate the physiological effects of tetracycline antibiotics on aquatic life. Results showed that the degree of toxicities of the following target antibiotics was TC (tetracycline hydrochloride) > CTC (chlortetracycline hydrochloride) > OTC (oxytetracycline hydrochloride) in terms of growth parameters, EC10 (0.63, 1.86, and 3.02 mg/L, respectively), and EC20 (1.58, 4.09, and 4.86 mg/L, respectively) values. These antibiotics inhibited the production of microcystin-LR (MC-LR) to varying degrees. CTC interfered M. aeruginosa cells and decreased their ability to release MC-LR, but this antibiotic stimulated the ability of these cells to synthesize MC-LR at 2 and 5 mg/L. OTC elicited a relatively weaker toxicity than CTC did and reduced MC-LR release. TC was the most toxic among the three antibiotics, and this antibiotic simultaneously reduced intracellular and extracellular MC-LR equivalents. Our results helped elucidate the effects of tetracycline antibiotics on M. aeruginosa, which is essential for environmental evaluation and protection. Our results are also helpful for guiding the application of veterinary antibiotics in agricultural settings.
Highlights
Veterinary antibiotics are biologically active molecules that are widely administered as therapeutics and growth promoters in livestock production and feed additives in fish farms; these molecules are used to prevent crop damage induced by bacteria [1]
Our study aimed to evaluate the toxic effects of tetracycline antibiotics on aquatic organisms to obtain information on the risks involved in the release of these drugs into the environment
The present study found that chlortetracycline hydrochloride (CTC), OTC and tetracycline hydrochloride (TC) interfered the production of MC-LR to different degrees, with different manners, and most MC-LR equivalents mainly in the intracellular fraction at 48 h of exposure
Summary
Veterinary antibiotics are biologically active molecules that are widely administered as therapeutics and growth promoters in livestock production and feed additives in fish farms; these molecules are used to prevent crop damage induced by bacteria [1]. Federation of Animal Health, more than 4,700 tonnes of antibiotics were administered to farm animals in 1999 in the European Union (EU) [2]. The annual consumption of antibiotics by livestock in the USA is approximately 11,000 tonnes [3]. In China, 15,770 tonnes of antibiotics were used as non-prescription therapeutics in 2004 [4]. The annual global usage of antibiotics has been estimated between 100,000 and. 200,000 tonnes globally [5], and this amount has increased in many developed and developing nations.
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